This invention relates to vacuum envelopes, and more particularly, to a vapor shield supporting ring for such envelopes and to the method of installing such supporting rings.
In vacuum devices, such as circuit interrupters, the metallic vapors that are produced by arcing between the contacts often condense on the insulating envelope of the device. As is well understood, these vapors tend to form a metallic coating which may cause the device to fail. To protect these devices from such metal depositions on the envelope, metal shields are often provided about the contacts such as, for example, the shield disclosed in U.S. Pat. No. 3,048,681 in the name of George Polinko, Jr., and assigned to the same assignee as this invention. Often such shields are held in place by pins or the like extending through the envelope or embedded in the glass, in the manner taught by U.S. Pat. No. 3,048,681. However, the use of such pins leads to problems in obtaining proper alignment or orientation of the pin as well as increasing the cost of manufacture of such vacuum devices.
To overcome such problems, it is known to embed a support ring in the vacuum envelope during the casting or molding of such envelope. A ring so embedded is described and claimed in U.S. Pat. No. 3,376,186 in the name of Lucek et al one of the inventors herein, and assigned to the same assignee as this invention. One of the undesirable features of the support ring of U.S. Pat. No. 3,376,186 is that the ring protrudes beyond the exterior of the envelope. This extension of the edge of the ring beyond the exterior of the envelope is caused in part by the means of embedding of such ring in the envelope, as is described and claimed in U.S. Pat. No. 3,376,186. It is desirable to provide a support of mounting ring for a vapor shield, which is embedded in the envelope, extending into the interior thereof, but which does not extend to the outer surface of the envelope.
An object of this invention is to provide a vacuum envelope having a supporting ring embedded therein but which does not extend to the outer surface of the envelope.
A further object of this invention is to provide a supporting ring in the vacuum envelope wherein the glass of the envelope is continuous along the exterior circumference of such supporting ring.